Pt and Pd in sediments from the Pearl River Estuary, South China: background levels, distribution, and source.

PURPOSE: This study assessed the concentrations of platinum (Pt) and palladium (Pd) in surface sediments and sedimentary cores collected from the Pearl River Estuary with a view of evaluating the distribution, background levels, possible sources, and contamination level of anthropogenic Pt and Pd. MATERIALS AND METHODS: Thirty-six samples of surface sediments and 12 samples from sedimentary cores were collected. Al(2)O(3) was analyzed on fused glass disks by X-ray fluorescence spectrometer. Heavy metal elements were measured by inductively coupled plasma-mass spectrometry. Pt and Pd were separated from the sample matrix by anion exchange chromatography and subsequent solvent extraction after samples had been digested in Carius tubes using aqua regia. The analysis of Pt and Pd was performed by isotopic dilution-inductively coupled plasma-mass spectrometry. RESULTS AND DISCUSSION: Pt and Pd concentrations in surface sediments were 0.28-2.11 and 0.39-38.30 ng/g, respectively, and Pt and Pd concentrations in sedimentary cores were 0.19-1.18 and 0.15-1.76 ng/g, respectively. Background values of Pt and Pd were 0.20-1.17 and 0.10-1.34 ng/g, respectively. The spatial distribution of the enrichment factor differed between Pt and Pd in surface sediments. Down-core variations in Pt, Pd, and other heavy metal elements were similar in all cases and were related to sediment type. CONCLUSIONS: Some of the Pt and Pt in surface samples were derived from anthropogenic emissions. Pt and Pd were delivered to the sediment by fluvial input. In addition to vehicle exhaust catalysts, Pt and Pd were derived from other sources (e.g., industrial process). An important post-burial remobilization process of Pt and Pd is likely to be particle mixing by billows caused by typhoon.

Determination of rhenium content in molybdenite by ICP-MS after separation of the major matrix by solvent extraction with N-benzoyl-N-phenylhydroxalamine.

A simple and rapid analytical method for determining the concentration of rhenium in molybdenite for Re-Os dating was developed. The method used isotope dilution-inductively coupled plasma-mass spectrometry (ID-ICP-MS) after the removal of major matrix elements (e.g., Mo, Fe, and W) from Re by solvent extraction with N-benzoyl-N-phenylhydroxylamine (BPHA) in chloroform solution. The effect on extraction efficiency of parameters such as pH (HCl concentration), BPHA concentration, and extraction time were also assessed. Under the optimal experimental conditions, the validity of the separation method was accessed by measuring (187)Re/(185)Re values for a molybdenite reference material (JDC). The obtained values were in good agreement with previously measured values of the Re standard. The proposed method was applied to replicate Re-Os dating of JDC and seven samples of molybdenite from the Yuanzhuding large Cu-Mo porphyry deposit. The results demonstrate good precision and accuracy for the proposed method. The advantages of the method (i.e., simplicity, efficiency, short analysis time, and low cost) make it suitable for routine analysis.

[A noninvasive model to predict histological liver cirrhosis in patients with chronic hepatitis B].

OBJECTIVE: To construct a noninvasive model to predict histological liver cirrhosis in patients with chronic hepatitis B. METHODS: 275 patients with chronic hepatitis B were divided into a training group (206 cases) and a validation group (69 cases). The constituent ratios of patients in the fibrosis stages S0-S3, fibrosis stage S4 (early cirrhosis) and active cirrhosis stage were calculated according to the liver biopsy results. 30 noninvasive variables, including age-platelet index (API), aspartate aminotransferase to platelet ratio index (APRI), spleen-platelet ratio index (SRPI) and age-spleen-platelet ratio index (ASPRI), were analyzed by univariate analysis and multivariate logistic regression. Variables that were significantly different between patients with and without cirrhosis were used to construct a noninvasive prediction model, and the model was then tested in the validation group. RESULTS: (1) Of the 275 patients with chronic hepatitis B, 193 (70.2%) were in the fibrosis stages S0-S3, 42 (15.3%) in fibrosis stage S4, 40 (14.5%) in active cirrhosis stage. (2) There were 23 variables that are significantly different between patients with and without cirrhosis by univariate analysis. The 23 variables were further analyzed by multivariate logistic regression, and 4 independent factors, including international normalized ratio (INR), gamma glutamyltranspeptidase (GGT), ASPRI, hepatitis B e antigen (HBeAg) were used to construct a noninvasive prediction model. (3) By receiver operating characteristic curves (ROC) analysis, to discriminate patients in stages S0-S3 from patients in stage S4 and patients in active cirrhosis stage, the area under ROC (AUROC), cut-off value, sensitivity, specificity and accuracy of the model were 0.871, 0.458, 84.4%, 75.7%, and 79.7% respectively. To discriminate patients in active cirrhosis stage from patients in other stages, the AUROC, cut-off value, sensitivity, specificity and accuracy were 0.753, 0.526, 81.8%, 62.9%, and 67.4% respectively. There was no significant difference in AUROC between the training group and the validation group (P less than 0.05). CONCLUSION: INR, GGT, ASPRI and HBeAg are associated with early cirrhosis and active cirrhosis. Our model can be used to predict early cirrhosis and active cirrhosis.